1. Field of the Invention
The present invention relates to ink jet printers. In particular, the invention relates to an apparatus for collecting ink mist associated with the printers and, as a result, enhances the reliability of the ink jet printers. The invention further relates to devices used with such printers to eliminate the contamination of printer components.
2. Prior Art
The use of ink jet printers for printing information on recording media is well known in the prior art. Conventional ink jet printers may be either of the electrical or magnetic type. The electrical type printers incorporate a plurality of electrical components and fluidic components. The components coact to perform the printing function.
The fluidic components include a drop generator having a chamber for affecting drop inducing vibration on a printing fluid or ink, and a nozzle plate with one or more ink nozzles interconnected to the chamber. A gutter assembly is positioned downstream from the nozzle plate in the flight path of ink droplets. The gutter assembly catches ink droplets which are not needed for printing on the recording medium.
In order to create the ink droplets, an electrical transducer is disposed within the drop generator. The transducer vibrates at a frequency which forces thread-like streams of ink which are initially ejected from the nozzles to be broken up into a series of constant size ink droplets at a point within the vicinity of the nozzle plate. A charge electrode is positioned along the flight path of the ink droplets. The function of the charge electrode is to selectively induce a charge on the ink droplets as said droplets separate from the streams. A pair of deflection plates is positioned downstream from the electrodes. The function of the deflection plates is to deflect a charged ink droplet either into the gutter or onto the recording media.
The magnetic type printers include magnetic components and fluidic components. Since magnetic type ink jet printers are well known in the prior art, a detailed description will not be given. Suffice it to say that the various magnetic and fluidic components are configured in a manner substantially similar to the components of the previously described electrical type ink jet printers.
One of the most pressing problems associated with ink jet printers of the above-described type is system reliability. The reliability problem is the result of contaminants coacting with the various components of the ink jet printing system to adversely affect system performance. The contaminants are usually of two kinds; the so-called ink dust or ink mist and foreign matter such as paper dust, debris, etc. The latter kind of contaminants are often referred to as airborne contaminants.
As was pointed out above, ink jet printing results from controlled ink droplets impinging on the recording surface. The droplets are usually propelled at a relatively high speed towards the recording surface. As the droplets impact the surface, small particles break off from the ink droplets and diffuse in various directions. The small particles are often referred to as ink dust or ink mist. The ink mist permeates the entire ink jet printing system and attaches to the print drum, recording paper, drum sensor, deflection plates, charge plate and other components. As the ink mist accumulates on the electrical components, the electrical characteristics are affected and, as a result, the ink jet system operates erroneously or breaks down. Additionally, the ink mist tends to cause undersirable markings, such as streaking on the recording paper or surface.
In addition to the ink mist, external contaminants such as paper dust fibers, particles of dirt and other materials permeate the normal atmosphere or surroundings in which an ink jet system operates. The external contaminants tend to settle on the nozzle plate of the drop generator, the charge electrode and the deflection plates. Contaminants on the charge electrode and the deflection plates tend to affect the electrical characteristics of those components. Likewise, contaminants on the nozzle plates tend to clog the minute orifices through which ink is issued for printing on the recording surface.
U.S. Pat. No. 3,981,020 describes a device used in the prior art to solve the ink mist problem. The device consists of an electrode means which is arranged in a position suitable for substantially removing the diffused ink mist from the ink jet system printer with the use of a controlled electrostatic force. The electrode means is positioned relative to the deflection electrode at a predetermined distance away from the front surface of the recording paper. The electrode means is supplied with a controlled voltage. The voltage is of the same polarity as that of the charged ink mist. Since the charge on the electrode means and the charge on the ink mist are identical, an electrostatic repulsive force is developed between the ink mist and the electrode means. The force repels the ink dust towards the paper and away from the deflection plate.
It should be noted that the above-described apparatus is geared primarily to prevent ink mist from contacting the deflection electrodes. It does not afford protection to the other components of the ink jet printer system or prevent smudging of the recording paper.
U.S. Pat. No. 4,024,548 is another example of the prior art devices used to collect ink mist associated with an ink jet printer. The ink mist absorbing device consists of a laminated member mounted between the drum carrying the recording medium and the ink jet printer system. The laminated member is formed from two porous materials having different degrees of porosity. An opening is fabricated in the laminated member and the droplets are propelled through the opening. Ink mist reverberating from the recording surface is absorbed by the porous material facing said surface. It is worthwhile noting that the ink mist device is a passive device and has to be replaced periodically.
IBM.RTM. Technical Disclosure Bulletin, Vol. 17, No. 8, January 1975, Pg. 2256, describes a combined ink jet gutter and mist shield device. The device is formed by two blocks joined together by a pedestal. A plurality of ink collecting channels and conducting ducts are formed on one surface of the blocks. The opposite surface of the blocks is planar and acts as a mist shield to prevent ink mist from contaminating the printer components. An electrode may be plated on the planar surface to attract the ink mist as the mist reverberates from the recording surface.
IBM.RTM. Technical Disclosure Bulletin, Vol. 17, No. 9, February 1975, pgs. 2622-2623 describes a cassette ink jet head with an ink mist shield.
IBM.RTM. Technical Disclosure Bulletin Vol. 17, No. 10, March 1975, pgs. 3022-3023 describes the use of an absorbant wiper for cleaning the ink mist from the deflection electrodes.
IBM.RTM. Technical Disclosure Bulletin, Vol. 18, No. 9, February 1976, pgs. 2941-2942 describes a device for collecting ink splatter and paper dust. The device consists of a tank with a side wall extending upwardly to form a collecting plate. The orientation between the device and the ink jet printing system is such that the upwardly extending collection plate is disposed between the surface on which data is recorded and the other components of the printer. A wicking layer is disposed on the surface of the plate facing the recording surface. Oil from the tank permeates the layer. Ink splatter is collected by the oil soaked layer and is returned to the tank where it is separated from the oil and is collected into another tank.